1. Field of the Invention
The present invention relates to a fluid monitoring apparatus of a compact and modular character, including field-replaceable components.
2. Description of the Related Art
In the manufacture of microelectronic devices, a variety of process tools are employed, having chambers that require cleaning to remove deposited materials from wall surfaces and internal structures of such chambers. Process tools, as such term is used herein, refers to apparatus that is utilized to conduct unit operations in microelectronic device manufacture, such as chemical vapor deposition, physical vapor deposition, etching, ion implantation, etc.
Various nitrides, including silicon nitride, titanium nitride, and tantalum nitride, are used in semiconductor processing as interlayer dielectrics and diffusion barriers. Post-processing deposit removal from the process tool is critical to ensure that deposits do not disengage, e.g., flake away, and contaminate the surface of a wafer during subsequent active processing, since such contamination can render the resulting microelectronic device product deficient or even useless for its intended purpose. Further, the chamber may include specialized components, such as collimators, shields, electrostatic chucks, etc., whose utility can be compromised by such deposits.
Accordingly, a variety of cleaning reagents and cleaning processes have evolved to address the need for removing unwanted deposits from microelectronic manufacturing tools and substrates on which such deposits are present. For example, fluorocompound cleaning compositions are available and may be used in ionized, e.g., plasma, forms to achieve removal of deposits from surfaces in the process tool.
In such cleaning operations, silicon nitride deposits are known to be particularly difficult to remove, in relation to other deposits, such as silicon or silicon oxides. As a result, the conventional approach to cleaning process chambers containing silicon nitride deposits has been to extend the clean time of the chamber, to thereby increase the effectiveness of the cleaning operation.
This approach, however, consumes expensive source gases, and typically does not achieve complete removal. As a result of such incomplete cleaning, system performance is compromised. For example, vapor deposition process tools may use showerhead vapor feed devices in the process chamber, and incomplete cleaning of the chamber and its internal components means that the expensive showerhead must be replaced regularly because nitride deposits are not removed and eventually accumulate to a point that the showerhead openings become plugged, rendering the showerhead useless for delivery of deposition reagents.
To address this problem, various effluent monitoring systems have been employed to determine the end point of the cleaning operation. For example, the endpoint monitor may be arranged to sense specific deposit or contaminant species in the process chamber that are removed by the cleaning operation, so that when such components are no longer sensed in the effluent, the endpoint monitor is effective to output a signal indicative of such endpoint having been reached in the cleaning operation.
The art continues to seek improved end point monitoring systems applicable to process tool cleaning operations.